1. Field of the Invention
The present invention relates generally to atomizers and more specifically it relates to an atomizer for thermal management system for efficiently thermally managing one or more heat producing devices.
2. Description of the Related Art
Modern electronic devices (e.g. microprocessors, circuit boards, power supplies and other electronic devices) have increased thermal management requirements. Conventional dry thermal management technology (e.g. fans, vents) simply is not capable of efficiently cooling modern high-end electronics. Spray cooling technology is being adopted today as the most efficient option for thermally managing electronic systems. U.S. Pat. No. 5,220,804 entitled High Heat Flux Evaporative Spray Cooling to Tilton et al. describes the earlier versions of spray technology. U.S. Pat. No. 6,108,201 entitled Fluid Control Apparatus and Method for Spray Cooling to Tilton et al. also describes the usage of spray technology to cool a printed circuit board. Spray thermal management may be performed locally (i.e. where the chip is sprayed directly), globally (i.e. where the chip and surrounding electronics/boards are also sprayed), a combination of locally and globally, or in conjunction with air cooling or other cooling methods.
Atomizers have been utilized for years within conventional spray cooling technologies for dispensing the liquid coolant as a fine spray upon one or more heat producing devices. A conventional atomizer typically is comprised of a housing with an orifice extend into the housing for dispensing the coolant in a fine spray onto the heat producing device. The orifice may be formed to various sizes and shapes to achieve a predetermined spray pattern and flow rate. U.S. Pat. Nos. 5,713,327 and 6,016,969 to Tilton are examples of alternative atomizers referred to as pressure swirl atomizers. A doctoral dissertation entitled “Spray Cooling” by Donald Tilton, 1989 (available through the University of Kentucky library system) describes how droplet size and momentum can create thin evaporative films capable of absorbing high heat fluxes. Generally, the thinner the film the greater the critical heat flux (CHF). If the dispensed droplets do not have sufficient momentum, they will be entrained by the vapor created by the thin-film and not contribute to cooling. If the dispensed droplets have too much momentum, they may cause splashing of the cooling surface.
One of the problems with conventional atomizers is that they do not allow for direct control of the coolant flow at the atomizer. The coolant flow through the orifice of a conventional atomizer is typically controlled by valves positioned between the atomizer and the pump. Hence, there is a specific volume and momentum of coolant contained within the conduit between the valve and the atomizer. The distance between the valve and atomizer creates unwanted system delay.
Another problem with conventional atomizers is that the coolant flow rate through each individual atomizer is controlled solely by the pressure of the coolant. The pressure can be controlled throughout the entire system through pump controls and valve controls; however the pressure cannot be easily controlled for each individual atomizer. Controlling atomizer pressures creates non-optimal droplet momentums; momentums necessary for high CHF's.
Another problem with conventional atomizers is that they are typically designed for a specific application and thermal management system. Conventional atomizers typically cannot be utilized in other thermal management system. In addition, if the characteristics of the heat producing device are changed requiring additional or reduced thermal management in specific locations, conventional atomizers do not provide the flexibility required to adjust accordingly.
A further problem with conventional atomizers is that they emit a constant spray upon the heat producing device. This constant spray upon the heat producing device may “flood” the surface of the heat producing device thereby reducing the thermal management efficiency during spray cooling.
Hence, there is a need for an atomizer for a spray cooling thermal management system that is individually controllable and that provides the flexibility required to thermally manage modern electronic devices.